This invention relates to regulated deflection circuits for television receivers, for example.
In typical television receiver circuitry, the horizontal deflection winding and a trace capacitor are series coupled. The trace capacitor is charged to a trace voltage from a B+ voltage supply through a flyback transformer primary winding. A trace switch then couples the trace capacitor and applies the capacitor's voltage across the deflection winding to generate a trace deflection current. During retrace, the trace switch is nonconductive and the deflection winding and flyback transformer primary winding resonate with a retrace capacitor to generate retrace pulse voltages in the two windings. During retrace, the deflection current reverses in direction preparatory to starting the next deflection interval. The retrace pulse voltage in the flyback transformer primary winding is stepped up by a high voltage winding to generate the high voltage or ultor accelerating potential.
To maintain a constant raster width, the trace voltage developed across the deflection winding and the retrace pulse voltages are regulated. To achieve this result, conventional television receiver regulators, using controllable semiconductor switching elements, develop a regulated B+ supply voltage derived from an unregulated input voltage, such as from a voltage derived from the AC line or mains supply. For greater efficiency, such switching elements typically operate at the relatively high frequencies of 16 or 20 kilohertz.
Other television receiver regulators couple the unregulated input voltage to the flyback transformer primary winding and to the deflection winding and trace capacitor. A second capacitor is coupled to the trace capacitor and is charged to a voltage which follows the input voltage variations. The trace voltage, established as the difference between the input voltage and the second capacitor voltage, is thereby regulated. The charge-discharge of the second capacitor occurs at the 16 kilohertz frequency of horizontal deflection. The voltage developed across the second capacitor is controlled, in part, by varying the current flow in an inductance coupled to the second capacitor. Such regulators are described in the U.S. patent application of W. Truskalo, Ser. No. 073040, concurrently filed herewith, entitled "REGULATED DEFLECTION CIRCUIT", and in the U.S. patent application of D. H. Willis, Ser. No. 06/058,659, filed July 19, 1979, entitled "REGULATED DEFLECTION CIRCUIT WITH REGULATOR SWITCH CONTROLLED BY DEFLECTION CURRENT", said Willis application being a continuation of Ser. No. 926,337 filed July 20, 1978, now abandoned.
The regulator in the aforementioned Truskalo and Willis applications may be required to regulate over relatively large input voltage variations, and accordingly may be required to vary the voltage across the second capacitor over a relatively large range of voltages. For example, in a typical transistorized horizontal deflection circuit, the trace voltage developed across the trace capacitor approximately equals +110 volts. For input voltages which vary between +180 volts and +120 volts, the voltage across the second capacitor must vary between +70 volts and +10 volts, a voltage ratio of 7 to 1. It is desirable to design a regulator with a range of regulation which can accommodate such large voltage variations.